The present invention relates to a cathode ray tube, and more particularly to a cathode ray tube having a. color selecting electrode.
A recent remarkable trend on the screen of a television receiver or the like is that the screen has become flat and large-sized, and that the definition of the screen has become high. In association with this trend, a plurality of metal tapes of a color selecting electrode constituting a part of a cathode ray tube used in the television receiver have become narrow in width and fine in pitch. Vibrations of the metal tapes constituting the color selecting electrode cause displacements of electron beams emitted from an electron gun provided in the cathode ray tube, causing color deviation. This phenomenon is remarkable particularly in a color selecting electrode having fine-pitched metal tapes. In general, a frame in the cathode ray tube is supported to a panel by four plate springs. The configuration of such a conventional cathode ray tube will now be described with reference to FIGS. 4 to 6.
FIG. 4 is a schematic sectional side view of a cathode ray tube 1, FIG. 5 is a schematic perspective view of a color selecting electrode 7 supported to a frame 3, and FIG. 6 is a schematic elevational view of the frame 3 supported to a panel 2a. 
As shown in FIGS. 4 to 6, the cathode ray tube 1 is composed generally of an integral glass tube consisting of a panel 2a, a funnel 2b, and a neck portion 2c, a rectangular frame 3 located inside the panel 2a, for supporting a color selecting electrode 7 of a thin sheet metal under tension, and an electron gun 6 located in the neck portion 2c. Four holders 8 are fixed at their one end to the outer side surface of the frame 3, and four plate springs 4 are fixed at one end to the other ends of the four holders 8, respectively. Each plate spring 4 is formed at its other end with an engaging hole 4a. The engaging holes 4a of the plate springs 4 are respectively engaged with four pins 5 provided on a skirt portion of the panel 2a, thus holding the frame 3 to the panel 2a. The color selecting electrode 7 includes a plurality of metal tapes 7a and a plurality of slits 7b. The metal tapes 7a and the slits 7b are alternatively arranged. Each metal tape 7a is supported to the frame 3 under a given tension. The frame 3 is composed of a pair of longer side members 3a and a pair of shorter side members 3b, and the tension is applied between the longer side members 3a. 
In many cases, a vibrating body such as a speaker is mounted in a television receiver or the like, and the vibration energy of the vibrating body is transmitted also to the color selecting electrode 7. In the case that the resonance frequency of the plate springs 4 supporting the frame 3 to the panel 2a (which will be hereinafter referred to simply as the resonance frequency of the plate springs 4) is equal or close to the resonance frequency of one of the plural metal tapes 7a, there is a possibility that the metal tape 7a whose resonance frequency is equal or close to the resonance frequency of the plate springs 4 may be resonated with a large amplitude, and also may vibrate the other peripheral metal tapes 7a and the entire color selecting electrode 7. As mentioned above, the vibrations of the metal tapes 7a cause color deviation due to the displacements of the electron beams emitted from the electron gun provided in the cathode ray tube. This phenomenon is remarkable particularly in the cathode ray tube 1 having the fine-pitched color selecting electrode 7 for a large screen with a high definition. Accordingly, making the resonance frequency of the plate springs 4 different from the resonance frequency of the metal tapes 7a is an important aspect in providing a cathode ray tube having vibration resistance.
It is accordingly an object of the present invention to provide a cathode ray tube having vibration resistance which can eliminate color deviation or the like.
According to the present invention, there is provided a cathode ray tube including a color selecting electrode having a plurality of metal tapes; a rectangular frame for holding the color selecting electrode under tension; a plate spring having one end fixed to the frame and the other end having an engaging hole; and a panel having means for engaging the engaging hole of the plate spring, the panel being held to the frame by the plate spring; wherein a resonance frequency of the plate spring is different from a resonance frequency of the metal tapes.
Preferably, the plate spring includes at least three plate springs for holding the panel to the frame. Further, the frame includes a pair of longer side members and a pair of shorter side members, and the tension is applied between the longer side members.
In the case of making the resonance frequency of the plate spring higher than the resonance frequency of the metal tapes, the plate spring preferably has a hardened film or a rib formed by drawing or bending so as to extend in a longitudinal direction of the plate spring. In the case of making the resonance frequency of the plate spring lower than the resonance frequency of the metal tapes, the plate spring preferably has a U-shaped bent portion, a V-shaped bent portion, a rectangular bent portion, a zigzag U-shaped bent portion, a zigzag V-shaped bent portion, or a zigzag rectangular bent portion.
The resonance frequency of the plate spring is different from the resonance frequency of the metal tapes constituting the color selecting electrode. Therefore, even when the cathode ray tube is vibrated by external vibration energy, there is no possibility that the metal tapes may be resonated with a large amplitude, so that it is possible to provide a cathode ray tube having vibration resistance which can eliminate color deviation or the like even though the color selecting electrode has a fine pitch with a high resolution.
Further, the resonance frequency of the plate spring can be set to a desired value by giving a suitable shape or the like to the plate spring. Accordingly, the cathode ray tube having vibration resistance can be easily manufactured.
Other objects and features of the invention will be more fully understood from the following detailed description and appended claims when taken with the accompanying drawings.